Thermal sensors usually use the change in resistance which occurs when temperature increases with absorbed infrared rays. Thermal sensors require complicated manufacturing processes and high manufacturing costs since temperature coefficient of resistance (TCR) of the material of the thermal image sensors is less than 2 to 3% and a microelectromechanical system (MEMS) structure and high-vacuum packaging are typically needed to obtain necessary sensitivity. Moreover, since the characteristics of the material are fixed, it is difficult to achieve an optimal design for the material according to application of, for example, the range of operating temperature.